So I noticed that the Old Man’s main theme, Gyaa Ha Ha! has an almost identical theme to the intro of Dio’s song Losing my Insanity. That song being fairly obscure, I wonder if Toby Fox might be a major Dio fan himself too. (Also here’s the link) Losing My Insanity - Dio
This is entirely possible but it’s also important to note how all of gerson themes are essentially just remixes of undyne’s themes in undertale (or lore-wise the other way around), but undynes themes could also be based off of it, albeit it’s a lot less likely. For example, “Gya Ha Ha!” Is a ‘remix’ of undynes “Ngahhh!!” Which sound a lot less likely the Dio song. I think it’s good chance that specifically Gersons theme was partially based off Dio though.
Holy yap I’m sorry for the wall of text
I’m not really hearing it to be honest. They have similar styles, sure, but to call them identical feels pretty far-fetched.